1. Field of the Invention
The present invention is in the field of windows and is directed more particularly to a thermal window construction having minimum heat transfer looses.
The invention is more particularly directed to an improved window of the type having two or more panes, a blind structure being interposed between the panes, the blind being shiftable between privacy and see-through configurations.
2. The Prior Art
With the increasing costs of energy, greater emphasis is placed upon the provision of window structures having minimal heat loss. Numerous expedients have been relied upon to reduce heat loss through window devices. Such expedients have included the provision of double pane windows, the frame portion of which has been formed either of a low conductivity material such as wood or plastic or, where high conductivity materials are used, the provision of a thermal break between inner and outer high conductivity components.
It is also known, in order to reduce convection losses resulting from currents generated within the space between the panes, to employ blind structures, such as Venetian blinds.
Desirably, such blind structures are adjustable to pass maximum radiation during the winter and minimum radiation during the summer.
U.S. Pat. Nos. 2,239,528 of Apr. 22, 1941 to Knudsen, 3,022,549 of Feb. 27, 1962 to Cummings, 4,076,068 of Feb. 28, 1978 to Archer, 4,091,592 of May 30, 1978 to Berlad, for example, pertain to blind structures interposed between the glass panes of a window structure. Such blind structures, when they are adjusted to their so-called see-through condition wherein the blades or slats defining the blind are essentially horizontally arrayed, tend to divide the space between the windows into a series of vertically stacked air spaces which reduce heat loss through convection to a greater degree than if the entire space between the panes were not subdivided.
From the standpoint of thermal efficiency, the blind structures heretofore known lose much of their convection impeding function when the same are shifted from a see-through to a privacy mode. The reason for such loss is that in the see-through mode the slats defining the blinds extend substantially across the entire space between the panes and function as an effective means for dividing the space into vertically stacked seals. However, as soon as the slats of the blinds are tilted to provide a privacy mode, the edge portions thereof are shifted away from the inner surface of the panes, with resultant formation of spaces adjacent the panes, with consequent increase in convective activity and resultant heat loss.